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Date November 2019 Marks available 2 Reference code 19N.3.hl.TZ0.15
Level HL Paper 3 Time zone TZ0
Command term Describe Question number 15 Adapted from N/A

Question

Describe the function of chlorophyll in photosynthesis.

[2]
a.

Compare and contrast the structures of starch and cellulose.

One similarity:

One difference:

[2]
b.

Explain why maltose, C12H22O11, is soluble in water.

[2]
c.

Markscheme

absorbs/traps light «energy» ✔

initiates redox reactions
OR
transfers electrons ✔

a.

One similarity:
1−4/glycosidic linkage
OR
glucose monomers/residues ✔

NOTE: Accept “both are polysaccharides”.

One difference:
starch has α-glucose AND cellulose has β-glucose «monomers»
OR
starch can form coiled/spiral/helical chains «and straight chains» AND cellulose cannot/can only form straight chains/can only form a linear structure
OR
starch «in amylopectin» also has 1−6 glycosidic links AND cellulose does not ✔

NOTE: Accept "cellulose has alternate glucose monomers upside down with respect to each other AND starch does not".

b.

«solubility depends on forming many» H-bonds with water ✔
maltose has many hydroxyl/OH/oxygen atom/O «and forms many H-bonds» ✔

NOTE: Reference to “with water” required.
Accept “hydroxy” for “hydroxyl” but not “hydroxide/OH”.
Reference to many/several OH groups/O atoms required for M2.

c.

Examiners report

[N/A]
a.
[N/A]
b.
[N/A]
c.

Syllabus sections

Options » B: Biochemistry » B.9 Biological pigments (HL only)
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Options » B: Biochemistry
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